Proceedings of the First Workshop Organized by the IAFSS Working Group on Measurement and Computation of Fire Phenomena (MaCFP).

This paper provides a report of the discussions held at the first workshop on Measurement and Computation of Fire Phenomena (MaCFP) on June 10-11 2017. The first MaCFP work-shop was both a technical meeting for the gas phase subgroup and a planning meeting for the condensed phase subgroup. The gas phase subgroup reported on a first suite of experimental- computational comparisons corresponding to an initial list of target experiments. The initial list of target experiments identifies a series of benchmark configurations with databases deemed suitable for validation of fire models based on a Computational Fluid Dynamics approach. The simulations presented at the first MaCFP workshop feature fine grid resolution at the millimeter- or centimeter- scale: these simulations allow an evaluation of the performance of fire models under high-resolution conditions in which the impact of numerical errors is reduced and many of the discrepancies between experimental data and computational results may be attributed to modeling errors. The experimental-computational comparisons are archived on the MaCFP repository [1]. Furthermore, the condensed phase subgroup presented a review of the main issues associated with measurements and modeling of pyrolysis phenomena. Overall, the first workshop provided an illustration of the potential of MaCFP in providing a response to the general need for greater levels of integration and coordination in fire research, and specifically to the particular needs of model validation.

Organic liquid mobility induced by smoldering remediation.

Laboratory column experiments plus analytical and numerical modeling together suggest that, under certain conditions, downward organic liquid mobilization can occur and impact smoldering behavior. This applies for organic liquids mixed with inert sand subjected to smoldering as thermal treatment. The observed effects include increased peak temperatures (here by up to 35%) and increased treatment times (here by up to 30%). Downward organic liquid migration occurs when (i) injected Darcy air flux is less than a threshold value (here less than 3cm/s), (ii) treatment systems are tall (here 90cm, not 30cm), and (iii) the organic liquid is temperature-sensitive (viscosity less than 0.01Pas at 150°C). The developed analytical equation provides the applied air flux that can negate the downwards organic liquid gradient required for migration. Smoldering behavior is demonstrated to adjust to liquid migration and thereby still destroy all the organic waste in the system. Smoldering is a relatively new, energy-efficient thermal treatment for organic liquid waste and these results are important for designing field applications of smoldering treatment.

Self-sustaining smoldering combustion: a novel remediation process for non-aqueous-phase liquids in porous media.

Smoldering combustion, the slow burning process associated typically with porous solids (e.g., charcoal), is here proposed as a novel remediation approach for nonaqueous phase liquids (NAPLs) embedded in porous media. Several one-dimensional vertical smoldering experiments are conducted on quartz sand containing fresh coal tar at an initial concentration of 71 000 mg/kg (approximately 25% saturation) and employing an upward darcy air flux of 4.25 cm/s. Following a short-duration energy input to achieve ignition at the lower boundary, a self-sustaining combustion front is observed to propagate upward at 1.3 x 10(-2) cm/s. The process is self-sustaining because the energy released during NAPL smoldering is efficiently trapped and recirculated by the soil matrix, preheating the NAPL ahead of the reaction front. The smoldering process is observed to self-terminate when all of the NAPL is destroyed or when the oxygen source is removed. Pre- and post-soil analysis revealed that NAPL smoldering reduced the concentration of total extractable petroleum hydrocarbons (TPH) from 38 000 mg/kg to below detection limits (< 0.1 mg/kg) throughout the majority of the column. A comparable experiment in which conductive heating is applied in the absence of smoldering demonstrates a 6-fold reduction in the net energy in the system and residual TPH values of 2000-35 000 mg/kg. A further repeat in which the air supply is prematurely terminated demonstrated that the NAPL smoldering process can be extinguished via external control. A suite of 23 demonstration experiments shows that NAPL smoldering is successful across a range of soil types (including simple layered systems) and contaminants (including laboratory mixtures of dodecane, DCA/ grease, TCE/oil, vegetable oil, crude oil, and mineral oil) as well as field-obtained samples of materials containing coal tar, oil drill cutting waste, and oil sands.

Ability of the Fire Propagation Apparatus to characterise the heat release rate of energetic materials.

Energetic materials encompass a wide range of chemical compounds. They react very rapidly releasing large amounts of energy. One of their peculiarities is that they carry an oxidizer and do not require oxygen from the air as their primary reaction partner. The aim of this paper is to present an analysis of the ability to estimate the heat release rate of a sample energetic material using two calorimetric methodologies. The methods are based on Oxygen Consumption and Carbon Dioxide Generation principles. Data have been obtained from experiments carried out with the Fire Propagation Apparatus. First, results from smoke powder combustion tests reveal significant discrepancies between the two approaches. Results from a sensitivity analysis realised in a previous work underlined that the most likely parameters to alter the heat release rate estimation are the energy constants and the concentration of oxygen. Correction procedures have been developed; one based on the estimation of the amount of oxygen supplied by the oxidizer, and a second one based on the calculation of new energy constants accounting for the chemical decomposition of the tested materials. Results are presented in this study.